Background: Tumors of the central nervous system (CNS) are a heterogeneous group of neoplasms with different prevalence in different sex and age groups and various parts of CNS. Objectives: Determining the relative frequency of different types of CNS tumors in different ages, sex and CNS anatomical locations. Materials and Methods: This retrospective study was performed using pathological reports of CNS tumors from patients in three main referral neurosurgical hospitals in Guilan, Iran from 1999 to 2009, which provided the following demographical data: patient age at the time of hospital admission, gender, histological diagnosis and the anatomical location of tumors. Results: From a total of 365 cases, 292 were brain tumors (80%) and the remaining 20% were diagnosed as spinal tumors. There were 27 different types of CNS tumors in the present study, with astrocytomas (28.5%) and meningiomas (27.1%) being the most common types among brain tumors and schwannomas (35.1%) being the most common among spinal cord tumors. Frontal lobe (17.5%) was the most common anatomical location for brain tumors, and thoracic region was the most common region affected by spinal cord tumors (41.1%). Metastatic or secondary tumors accounted for 3.8% of the CNS tumors in our study. Contrary to most other studies, the frequency of CNS tumors was higher in females than males and was most frequent in the 5th decade of life. Conclusions: This study demonstrated the high frequency of CNS tumors with astrocytic origin. The most common tumor was astrocytoma, with meningioma being the second most prominent one.